In many connections there is a need for impact attenuators, which can absorb and decelerate forces, in particular large forces as for example collision forces from vehicles. For example, this is the case at stationary structures such as safety barriers or crash barriers along roads and railways where it is desirable to decelerate the collision force gradually, partly for security reasons to protect passengers from injuries due to a too powerful retardation, but partly also for cost reasons to make it possible to design the safety barrier with comparatively small dimensions, which cannot withstand a momentarily deceleration of the collision force but which is capable of decelerating the force gradually along a somewhat longer distance. Thereby it is ensured that the safety barrier fulfills its purpose at the same time as the material consumption can be reduced and accordingly also the costs.
One problem with such impact attenuators is that they have to be durable, i.e. have to be in working order during years, maybe several decades of inactivity until someday an accident occurs and then they have to function without having been negatively affected during the lapse of time due to e.g. corrosion, intense contamination of dirt or the like which can make movable parts to jam and be completely blocked such that the function is jeopardized.